Present day automobile engines utilize a mixture of liquid fuel (gasoline) and air in the carburetor for burning in the engine. The basic problems associated with this approach include the following:
1. The liquid droplets mixed with the air tend to collect on the manifold walls whenever a change in direction occurs resulting in uneven distribution of the fuel to the cylinder. The uneven fuel distribution makes it necessary to enrich the mixture to ensure that the leanest cylinder receives a sufficient charge of fuel. The droplet collection tendency is further increased under increasing load and speed conditions which make it necessary to further enrich the mixture to compensate for the droplet collection in addition to the necessary enrichment for increasing load and speed. Such fuel enrichment results in decreased thermal efficiency and an increase in unburned hydrocarbons and carbon monoxide emitted in the exhaust gas.
2. Leaning the mixture to minimize the hydrocarbon and carbon monoxide emission results in a drastic loss of power compounded by the uneven distribution of fuel. Further, an increase in oxides of nitrogen emitted due to an increase in the average combustion chamber temperature results. Finally, there is a tendency to burn exhaust valves caused by the higher temperature of the exhaust gas passing the exhaust valve which results from the lower flame speed caused by the lean mixture.
The foregoing problem can be alleviated if fuel could be pre-vaporized rather than introduced in the form of a liquid or liquid droplets. U.S. Pat. No. 3,667,436 issued June 6, 1972 to Robert Reichhelm discloses a fuel gassification system for internal combustion engines. Essentially, Reichhelm feeds back part of the exhaust gases to heat and aid in vaporizing liquid fuel.